Optical lens

ABSTRACT

An optical lens includes a first lens group and a second lens group. The first lens group is disposed between a magnified side and a minified side and has a negative refractive power. The second lens group is disposed between the first lens group and the minified side and has a positive refractive power. The optical lens is capable of forming an image at the magnified side. F/H&gt;0.52, where F is an effective focal length, and H is an image height. A viewing angle is greater than 116.7 degrees.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims thepriority benefit of U.S. application Ser. No. 13/744,357, filed on Jan.17, 2013, now allowed, which claims the priority benefit of Taiwanapplication serial No. 101127292, filed on Jul. 27, 2012. The entiretyof each of the above-mentioned patent applications is herebyincorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention generally relates to a projection lens, and moreparticularly, to an optical lens.

2. Description of Related Art

In general, a long projection distance is required if a projector needsto project an image onto a large screen. Contrarily, a specialwide-angle lens is required to shorten the distance from the screen tothe projector if the image is to be projected onto the large screen froma short projection distance. That is, the wide-angle lens mayeffectively reduce the distance from the screen to the projector andproject a relatively large image. However, the aberration issue derivedfrom the wide-angle lens is one of the obstacles faced by designers.

There are a number of solutions to the aberration issue, e.g., throughthe use of plural aspheric lenses, the increase in the total length ofthe lens, the use of a number of lenses, and so on. For instance, inU.S. Pat. No. 6,621,645, at least one molded glass is applied, thusincreasing the costs. Besides, the distortion value disclosed in saidpatent is greater than ±1%. In U.S. Pat. No. 6,560,041, at least threeaspheric lenses are employed, which raises the manufacturing costs andthe assembly difficulty. If only a few aspheric lenses are to be used,and it is intended to effectively correct the aberration, the totallength of the lenses may be increased, and the volume of the projectionsystem may be enlarged. For instance, in U.S. Pat. No. 6,999,247 andU.S. Pat. No. 6,542,316, the total length of the lenses is greater than150 mm. It is also likely to correct the aberration by utilizing a largenumber of lenses. For instance, in U.S. Pat. No. 6,621,645 and U.S. Pat.No. 7,184,219, at least 14 lenses are applied in the projection lens foraberration correction. Besides, in Taiwan patent no. 1247915 and U.S.Pat. No. 7,952,817, at least 13 lenses are applied in the projectionlens for aberration correction.

In U.S. Pat. No. 7,423,819, the fixed-focus lens includes a first lensgroup, a second lens group, and a third lens group that are sequentiallyarranged from an object side to an image side, and the third lens groupincludes triple cemented lenses. U.S. Pat. No. 7,859,770 satisfies thefollowing: if F/H>0.627, the wide-angle effect may be achieved, and theaberration reaches the minimum value and satisfies 0.5<|F1/F|<1.7 and1.9<|F2/F|<3.1, where F refers to a focal length of the lens, F1 refersto a focal length of the first lens group, and F2 refers to a focallength of the second lens group. Lens-related technologies have alsobeen disclosed in numerous patents, such as U.S. Pat. No. 7,126,767,U.S. Pat. No. 7,123,426, and U.S. Pat. No. 7,173,777.

In view of the above, how to design a lens with low manufacturing costsand favorable imaging quality has become one of the research topics topeople having ordinary skill in the pertinent field.

SUMMARY OF THE INVENTION

The invention is directed an optical lens having low costs and favorableoptical characteristics.

Other aspects and advantages of the invention are set forth in thedescription of the techniques disclosed in the invention.

To achieve one of, a part of or all of the above-mentioned advantages,or to achieve other advantages, an embodiment of the invention providesan optical lens that includes a first lens group and a second lensgroup. The first lens group is disposed between a magnified side and aminified side and has a negative refractive power. The second lens groupis disposed between the first lens group and the minified side and has apositive refractive power. The optical lens is capable of forming animage at the magnified side. F/H>0.52, where F is an effective focallength, and H is an image height. A viewing angle is greater than 116.7degrees.

Another embodiment of the invention provides an optical lens thatincludes a first lens group and a second lens group. The first lensgroup is disposed between a magnified side and a minified side and has anegative refractive power. The second lens group is disposed between thefirst lens group and the minified side and has a positive refractivepower. The optical lens is capable of forming an image at the magnifiedside. 0.627>F/H>0.52, wherein F is an effective focal length, and H isan image height.

The embodiment of the invention has at least one of the followingadvantages or functions. The optical lens described in the embodiment ofthe invention includes two lens groups, which may effectively resolvethe aberration issue, reduce the volume of the projection system,simplify the fabrication and assembly of the lens, and significantlylower down the overall costs on optical devices and the costs on thelens mechanism.

Other features and advantages of the invention will be furtherunderstood from the further technological features disclosed by theembodiments of the invention wherein there are shown and describedembodiments of this invention, simply by way of illustration of modessuited to carry out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic view illustrating a structure of a fixed focallength lens according to a first embodiment of the invention.

FIG. 2 is a schematic view briefly illustrating an image processingdevice disposed on a minified side according to an embodiment of theinvention.

FIGS. 3-5 are diagrams showing imaging optical simulation data of thefixed focal length lens depicted in FIG. 1.

FIG. 6 is a schematic view illustrating a structure of a fixed focallength lens according to a second embodiment of the invention.

FIG. 7 is a schematic view illustrating a structure of a fixed focallength lens according to a third embodiment of the invention.

FIG. 8 is a schematic view illustrating a structure of a fixed focallength lens according to a fourth embodiment of the invention.

FIG. 9 is a schematic view illustrating a structure of a fixed focallength lens according to a fifth embodiment of the invention.

FIG. 10 is a schematic view illustrating a structure of a fixed focallength lens according to a sixth embodiment of the invention.

DETAILED DESCRIPTION OF DISCLOSED EXEMPLARY EMBODIMENTS

In the following detailed description of the embodiments, reference ismade to the accompanying drawings which form a part hereof, and in whichare shown by way of illustration specific embodiments in which theinvention may be practiced. In this regard, directional terminology,such as “top,” “bottom,” “front,” “back,” etc., is used with referenceto the orientation of the Figure(s) being described. The components ofthe invention can be positioned in a number of different orientations.As such, the directional terminology is used for purposes ofillustration and is in no way limiting. On the other hand, the drawingsare only schematic and the sizes of components may be exaggerated forclarity. It is to be understood that other embodiments may be utilizedand structural changes may be made without departing from the scope ofthe invention. Also, it is to be understood that the phraseology andterminology used herein are for the purpose of description and shouldnot be regarded as limiting. The use of “including,” “comprising,” or“having” and variations thereof herein is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional items.Unless limited otherwise, the terms “connected,” “coupled,” and“mounted” and variations thereof herein are used broadly and encompassdirect and indirect connections, couplings, and mountings. Similarly,the terms “facing,” “faces” and variations thereof herein are usedbroadly and encompass direct and indirect facing, and “adjacent to” andvariations thereof herein are used broadly and encompass directly andindirectly “adjacent to”. Therefore, the description of “A” componentfacing “B” component herein may contain the situations that “A”component directly faces “B” component or one or more additionalcomponents are between “A” component and “B” component. Also, thedescription of “A” component “adjacent to” “B” component herein maycontain the situations that “A” component is directly “adjacent to” “B”component or one or more additional components are between “A” componentand “B” component. Accordingly, the drawings and descriptions will beregarded as illustrative in nature and not as restrictive.

First Embodiment

FIG. 1 is a schematic view illustrating a structure of a fixed focallength lens according to a first embodiment of the invention. Withreference to FIG. 1, the fixed focal length lens 100 is suitable forbeing disposed between a magnified side and a minified side, and thefixed focal length lens 100 has an optical axis A and includes a firstlens group 110 and a second lens group 120.

The first lens group 110 has a negative refractive power and includes afirst lens G1, a second lens G2, and a third lens G3 sequentiallyarranged from the magnified side to the minified side. A refractivepower of the first lens G1, a refractive power of the second lens G2,and a refractive power of the third lens G3 are sequentially negative,negative, and negative. The second lens group 120 is disposed betweenthe first lens group 110 and the minified side and has a positiverefractive power. Besides, the second lens group 120 includes a fourthlens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, an eighthlens G8, a ninth lens G9, and a tenth lens G10 sequentially arrangedfrom the magnified side to the minified side. A refractive power of thefourth lens G4, a refractive power of the fifth lens G5, a refractivepower of the sixth lens G6, a refractive power of the seventh lens G7, arefractive power of the eighth lens G8, a refractive power of the ninthlens G9, and a refractive power of the tenth lens G10 are sequentiallypositive, positive, positive, negative, positive, negative, and positivefrom the magnified side to the minified side.

In the embodiment, the position of the second lens group 120 in thefixed focal length lens 100 is fixed, and the first lens group 110 movesrelative to the second lens group 120 to focus. Namely, the first lensgroup 110 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 130 may be disposed on theminified side. In the embodiment, the image processing device 130 is,for instance, a light valve, and the light valve may be a digitalmicro-mirror device (DMD), a liquid-crystal-on-silicon panel (LCOSpanel), or a transmissive liquid crystal panel (transmissive LCD), forinstance. Besides, in the embodiment, the fixed focal length lens 100 isused to form an image provided by the image processing device 130 at themagnified side.

In addition, as shown in FIG. 1, the fixed focal length lens 100described in the embodiment further includes an aperture stop ASdisposed between the eighth lens G8 and the ninth lens G9. A glass cover140 is further disposed between the image processing device 130 and thetenth lens G10 to protect the image processing device 130.

To ensure the optical imaging quality, the fixed focal length lens 100in the embodiment may satisfy 0.515<|f₁/f|<1.299 and 2.313<|f₂/f|<5.724.Here, f refers to an effective focal length (EFL) of the fixed focallength lens 100, f₁ refers to an EFL of the first lens group 110, and f₂refers to an EFL of the second lens group 120.

An embodiment of the fixed focal length lens 100 is given hereinafter.However, the invention is not limited to the data listed in Table 1.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 1 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 53.88 4.60 1.49 57.4 First lens S2 20.86 11.26 S344.82 2.40 1.74 44.8 Second lens S4 18.15 16.28 S5 −42.96 2.00 1.74 44.8Third lens S6 22.75 Variable S7 −262.48 3.08 1.78 25.7 Fourth lens S8−51.60 3.72 S9 32.08 8.38 1.60 38.0 Fifth lens S10 −70.77 14.20 S1117.81 4.70 1.52 64.1 Sixth lens S12 −20.08 4.59 1.83 37.2 Seventh lensS13 11.00 5.70 1.58 40.7 Eighth lens S14 −35.81 1.20 Aperture stop S1541.25 2.39 1.85 23.8 Ninth lens S16 19.36 3.90 1.50 81.5 Tenth lens S17−19.88 21.50

In Table 1, the interval refers to a linear distance between twoadjacent surfaces on the optical axis A. For instance, the interval ofthe surface S1 refers to the linear distance between the surface S1 andthe surface S2 on the optical axis A. The thickness, the refractionindex, and the abbe number corresponding to each of the lenses listed inthe “Notes” columns may be referred to as the corresponding values ofthe interval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 120 in the fixed focal length lens 100 remains unchanged, and thefirst lens group 110 moves relative to the second lens group 120 tofocus. Therefore, the interval of the surface S6 is marked as“variable”, which indicates the linear distance between the surface S6and the surface S7 is variable on the optical axis A. According to anembodiment, when a projection distance is relatively short, the intervalof the surface S6 is 8.83 mm, for instance; according to anotherembodiment, when a projection distance is relatively long, the intervalof the surface S6 is 8.76 mm, for instance.

Moreover, in Table 1, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurfaces S9 and S10 are two surfaces of the fifth lens G5, the surfaceS11 is a surface of the sixth lens G6 facing the magnified side, thesurface S12 is a surface where the sixth lens G6 is connected to theseventh lens G7, the surface S13 is a surface where the seventh lens G7is connected to the eighth lens G8, and the surface S14 is a surface ofthe eight lens G8 facing the minified side. Here, the surface S14 isalso the place where the aperture stop AS is located. The surface S15 isa surface of the ninth lens G9 facing the magnified side, the surfaceS16 is a surface where the ninth lens G9 is connected to the tenth lensG10, and the surface S17 is surface of the tenth lens G10 facing theminified side. The curvature radius, the interval, and other parametersof each surface are shown in Table 1 and will not be further describedhereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces andmay be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{1}} + {A_{2}y^{2}} + {A_{3}y^{3}} + {A_{4}y^{4}} + {A_{5}y^{5}} + {A_{6}y^{6}} + {A_{7}y^{7}} + {A_{8}y^{8}} + {A_{10}y^{10}} + {A_{11}y^{11}} + {A_{12}y^{12}} + {A_{13}y^{13}} + {A_{14}y^{14}}}$

In the formula, Z is a sag in the direction of the optical axis A, and cis the inverse of the radius of an osculating sphere, i.e. the inverseof the curvature radii (e.g., the curvature radii of the surfaces S1 andS2 in Table 1) close to the optical axis A. K is a conic coefficient, yis an aspheric height, and A₁ to A₁₄ are aspheric coefficients. Theparameter values of the surfaces S1 and S2 are listed in Table 2.

TABLE 2 Aspheric Conic Coefficient Coefficient Coefficient CoefficientParameter Coefficient K A₁ A₂ A₃ A₄ S1  9.46E−01 −9.37E−03 3.30E−03−5.00E−04 2.49E−05 S2 −6.27E−01 −4.93E−03 4.61E−03 −3.96E−04 1.60E−05Aspheric Coefficient Coefficient Coefficient Coefficient ParameterCoefficient A₅ A₆ A₇ A₈ A₉ S1 3.14E−08 −2.58E−08 −3.97E−11  2.63E−11−1.17E−14 S2 2.39E−07 −1.53E−08  1.32E−10 −2.98E−11 −1.53E−13 AsphericCoefficient Coefficient Coefficient Coefficient Parameter CoefficientA₁₀ A₁₁ A₁₂ A₁₃ A₁₄ S1 −1.69E−14  1.44E−17 6.21E−18 2.90E−21 −1.11E−21S2 −5.64E−15 −1.34E−16 5.10E−17 7.36E−20 −2.69E−20

According to the present embodiment, it may be learned that the firstlens G1 is an aspheric lens and thus the first lens G1 may effectivelyresolve coma issues, astigmatism issues, or distortion issues of thefixed focal length lens 100. Besides, in the embodiment, the optimalrange of the effective focal length (EFL) of the fixed focal length lens100 is 7.84 mm to 8.3 mm, which should however not be construed as alimitation to the invention. Besides, the numerical aperture (F/#)ranges from 2.71 to 2.91, and the viewing angle (2ω) is greater than116.6°.

Moreover, the fixed-focus lens 100 described herein satisfies F/H>0.52,where F is an EFL of the fixed focal length lens 100, and H is an imageheight. If F/H>1, the viewing angle (2ω) of the fixed focal length lens100 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 100 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

FIG. 2 is a schematic view briefly illustrating an image processingdevice disposed on a minified side according to an embodiment of theinvention. The viewing angle is defined by watching from the magnifiedside to the minified side of the fixed focal length lens 100. Theimaging process device 130 described in the embodiment is a light valve,and the light valve may be a DMD, for instance. The distance between theoptical axis A of the fixed focal length lens 100 and the lower-left endpoint of the image processing device 130 may be defined as the imageheight H described herein. A circumscribed circle with the optical axisA as the circle center and the image height H as the radius may be made,and the circumscribed circle passes through the two lower end points ofthe image processing device 130.

With reference to FIG. 1, in the first lens group 110 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, andthe third lens G3 is a biconcave lens. Each of the second lens G2 andthe third lens G3 is a spherical lens, for instance. Due to thecompensation resulting from the aspheric lens in the first lens group110, at least the distortion issue may be effectively resolved.

According to the embodiment, in the second lens group 120, the fourthlens G4 is a concave-convex lens with a convex surface facing theminified side, each of the fifth lens G5, the sixth lens G6, the eighthlens G8, and the tenth lens G10 is a biconvex lens, the seventh lens G7is a biconcave lens, and the ninth lens G9 is a convex-concave lens witha convex surface facing the magnified side. In the second lens group120, the sixth lens G6, the seventh lens G7, and the eighth lens G8together form a triple cemented lens 122, and the ninth lens G9 and thetenth lens G10 together form a double cemented lens 124. Thereby, thespherical aberration issue, the field curvature issue, and the coloraberration issue of the fixed focal length lens 100 may be effectivelyresolved. Moreover, the lenses in the second lens group 120 are allspherical lenses, for instance. Since the tenth lens G10 is the biconvexlens, the light at the minified side may be effectively collected, andthe collected light may pass through the lenses and be projected on themagnified side.

FIGS. 3-5 are diagrams showing imaging optical simulation data of thefixed focal length lens 100 depicted in FIG. 1. The simulation isconducted on three reference wavebands, i.e., red light with thewavelength of 656 nm, green light with the wavelength of 588 nm, andblue light with the wavelength of 486 nm. Please refer to FIG. 3 to FIG.5. FIG. 3 is a transverse ray fan plot, wherein the x axis representsthe position where the light passes through the aperture stop AS, andthe y axis represents the position where the light strikes onto theimage plane (e.g., the light valve 130). FIG. 4 shows the plot of thedistortion. FIG. 5 is a lateral color diagram, wherein the abscissarepresents the distance from an intersection of the primary lights withthree wavelengths on the imaging plane to the intersection of theprimary light with the central wavelength on the imaging plane, and theordinate represents a field radius. Since everything shown in FIG. 3 toFIG. 5 falls within a standard range, the fixed focal length lens 100described in this embodiment may have favorable imaging quality.

Second Embodiment

FIG. 6 is a schematic view illustrating a structure of a fixed focallength lens according to a second embodiment of the invention. Withreference to FIG. 6, the fixed focal length lens 600 is suitable forbeing disposed between a magnified side and a minified side, and thefixed focal length lens 600 has an optical axis A and includes a firstlens group 610 and a second lens group 620.

The first lens group 610 has a negative refractive power and includes afirst lens G1, a second lens G2, and a third lens G3 sequentiallyarranged from the magnified side to the minified side. A refractivepower of the first lens G1, a refractive power of the second lens G2,and a refractive power of the third lens G3 are sequentially negative,negative, and negative. The second lens group 620 is disposed betweenthe first lens group 610 and the minified side and has a positiverefractive power. Besides, the second lens group 620 includes a fourthlens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, an eighthlens G8, a ninth lens G9, and a tenth lens G10 sequentially arrangedfrom the magnified side to the minified side. A refractive power of thefourth lens G4, a refractive power of the fifth lens G5, a refractivepower of the sixth lens G6, a refractive power of the seventh lens G7, arefractive power of the eighth lens G8, a refractive power of the ninthlens G9, and a refractive power of the tenth lens G10 are sequentiallypositive, positive, positive, negative, positive, negative, and positivefrom the magnified side to the minified side.

In the embodiment, the position of the second lens group 620 in thefixed focal length lens 600 is fixed, and the first lens group 610 movesrelative to the second lens group 620 to focus. Namely, the first lensgroup 610 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 630 may be disposed on theminified side. The imaging process device 630 described in theembodiment is a light valve, and the light valve may be a DMD, an LCOSpanel, or a transmissive LCD, for instance. Besides, in the presentembodiment, the fixed-focus lens 600 is adapted for imaging an imageprovided by the image processing device 630 at the magnified side.

In addition, as shown in FIG. 6, the fixed focal length lens 600described in the embodiment further includes an aperture stop ASdisposed between the eighth lens G8 and the ninth lens G9. A glass cover640 is further disposed between the image processing device 630 and thetenth lens G10 to protect the image processing device 630.

To ensure the optical imaging quality, the fixed-focus lens 600 in theembodiment may satisfy 0.515<|f₁/f|<1.299 and 2.313<|f₂/f|<5.724. Here,f refers to an EFL of the fixed focal length lens 600, f₁ refers to anEFL of the first lens group 610, and f₂ refers to an EFL of the secondlens group 620.

An embodiment of the fixed focal length lens 600 is given hereinafter.However, the invention is not limited to the data listed in Table 3.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 3 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 74.73 4.76 1.49 57.44 First lens S2 21.16 13.76 S349.53 2.00 1.74 44.79 Second lens S4 18.26 12.98 S5 −52.91 2.63 1.7444.79 Third lens S6 23.34 Variable S7 375.11 3.85 1.69 31.08 Fourth lensS8 −58.67 10.39 S9 30.83 6.93 1.60 39.24 Fifth lens S10 −85.27 12.58 S1114.34 4.07 1.49 70.24 Sixth lens S12 −17.98 2.50 1.83 37.16 Seventh lensS13 6.96 3.24 1.73 28.46 Eighth lens S14 71.99 1.00 Aperture stop S1534.61 2.41 1.85 23.78 Ninth lens S16 10.03 3.91 1.58 59.03 Tenth lensS17 −14.15 21.50

In Table 3, the interval refers to a linear distance on the optical axisA between two adjacent surfaces. For instance, the interval of thesurface S1 refers to the linear distance between the surface S1 and thesurface S2 on the optical axis A. The thickness, the refraction index,and the abbe number corresponding to each of the lenses listed in the“Notes” columns may be referred to as the corresponding values of theinterval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 620 in the fixed focal length lens 600 remains unchanged, and thefirst lens group 610 moves relative to the second lens group 620 tofocus. Therefore, the interval of the surface S6 is marked as“variable”, which indicates the linear distance on the optical axisbetween the surface S6 and the surface S7 is variable. According to anembodiment, when a projection distance is relatively short, the intervalof the surface S6 is 9.46 mm, for instance; according to anotherembodiment, when a projection distance is relatively long, the intervalof the surface S6 is 9.37 mm, for instance.

Moreover, in Table 3, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurfaces S9 and S10 are two surfaces of the fifth lens G5, the surfaceS11 is a surface of the sixth lens G6 facing the magnified side, thesurface S12 is a surface where the sixth lens G6 is connected to theseventh lens G7, the surface S13 is a surface where the seventh lens G7is connected to the eighth lens G8, and the surface S14 is a surface ofthe eight lens G8 facing the minified side. Here, the surface S14 isalso the place where the aperture stop AS is located. The surface S15 isa surface of the ninth lens G9 facing the magnified side, the surfaceS16 is a surface where the ninth lens G9 is connected to the tenth lensG10, and the surface S17 is surface of the tenth lens G10 facing theminified side. The numeral values of the parameters, such as thecurvature radius and the interval of each surface, are given in Table 3and thus will not be repeated hereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces andmay be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{1}} + {A_{2}y^{2}} + {A_{3}y^{3}} + {A_{4}y^{4}} + {A_{5}y^{5}} + {A_{6}y^{6}} + {A_{7}y^{7}} + {A_{8}y^{8}} + {A_{10}y^{10}} + {A_{11}y^{11}} + {A_{12}y^{12}} + {A_{13}y^{13}} + {A_{14}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S1 and S2 in Table 3) close to the optical axis A. K is a coniccoefficient, y is an aspheric height, and A₁ to A₁₄ are asphericcoefficients. The parameter values of the surfaces S1 and S2 are listedin Table 4.

TABLE 4 Aspheric Conic Coefficient Coefficient Coefficient CoefficientParameter Coefficient K A₁ A₂ A₃ A₄ S1  1.01223 −5.84E−05  9.93E−05−1.21E−07 1.47E−05 S2 −0.58300 −5.99E−05 −4.12E−05  6.90E−07 1.66E−05Aspheric Coefficient Coefficient Coefficient Coefficient ParameterCoefficient A₅ A₆ A₇ A₈ A₉ S1 −2.88E−09 −2.47E−08 6.19E−12  2.72E−11−5.77E−15 S2 −3.72E−09 −2.28E−08 1.21E−11 −2.90E−11 −1.88E−14 AsphericCoefficient Coefficient Coefficient Coefficient Parameter CoefficientA₁₀ A₁₁ A₁₂ A₁₃ A₁₄ S1 −1.71E−14 2.81E−18 5.84E−18 −6.09E−22 −6.79E−22S2 −1.06E−18 1.17E−17 5.29E−17 −2.26E−21 −3.40E−20

According to the present embodiment, it may be learned that the firstlens G1 is an aspheric lens and thus the first lens G1 may effectivelyresolve coma issues, astigmatism issues, or distortion issues of thefixed focal length lens 600. Besides, in the embodiment, the optimalrange of the EFL of the fixed focal length lens 600 is 7.24 mm to 7.27mm, which should however not be construed as a limitation to theinvention. Besides, the numerical aperture (F/#) is 2.79, and theviewing angle (2ω) is greater than 116.6°.

The surface S17 of the tenth lens G10 is an aspheric surface with evenpower and may be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{4}} + {A_{2}y^{6}} + {A_{3}y^{8}} + {A_{4}y^{10}} + {A_{5}y^{12}} + {A_{6}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurface S17 in Table 3) close to the optical axis A. K is a coniccoefficient, y is an aspheric height, and A₁ to A₆ are asphericcoefficients. Table 5 lists the parameter values of the surface S17.

TABLE 5 Conic Aspheric Coefficient Coefficient Coefficient CoefficientCoefficient Coefficient Coefficient Parameter K A₁ A₂ A₃ A₄ A₅ A₆ S17 0−1.67E−05 −6.49E−07 −5.70E−11 −6.38E−10 −2.81E−12 7.86E−14

Moreover, the fixed focal length lens 600 described herein satisfiesF/H>0.52, where F is an EFL of the fixed focal length lens 600, and H isan image height. The definition of the image height H may be referred toas that depicted in FIG. 2 and thus will not be further describedhereinafter. If F/H>1, the viewing angle (2ω) of the fixed focal lengthlens 600 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 600 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

With reference to FIG. 6, in the first lens group 610 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, andthe third lens G3 is a biconcave lens. Each of the second lens G2 andthe third lens G3 is a spherical lens, for instance. Due to thecompensation resulting from the aspheric lens in the first lens group610, at least the distortion issue may be effectively resolved.

According to the present embodiment, in the second lens group 620, eachof the fourth lens G4, the fifth lens G5, the sixth lens G6, and thetenth lens G10 is a biconvex lens, the seventh lens G7 is a biconcavelens, the eighth lens G8 is a concave-convex lens with a convex surfacefacing the magnified side, and the ninth lens G9 is a convex-concavelens with a convex surface facing the magnified side. In the second lensgroup 620, the sixth lens G6, the seventh lens G7, and the eighth lensG8 together form a triple cemented lens 622, and the ninth lens G9 andthe tenth lens G10 together form a double cemented lens 624. Thereby,the spherical aberration issue, the field curvature issue, and the coloraberration issue of the fixed focal length lens 600 may be effectivelyresolved. Besides, the tenth lens G10 is an aspheric lens. Aside fromthe tenth lens G10, other lenses of the second lens group 620 arespherical lenses, for instance. Since the tenth lens G10 is the biconvexlens, the light at the minified side may be effectively collected, andthe collected light may pass through the lenses and be projected on themagnified side.

Third Embodiment

FIG. 7 is a schematic view illustrating a structure of a fixed focallength lens according to a third embodiment of the invention. Withreference to FIG. 7, the fixed focal length lens 700 is suitable forbeing disposed between a magnified side and a minified side, and thefixed focal length lens 700 has an optical axis A and includes a firstlens group 710 and a second lens group 720.

The first lens group 710 has a negative refractive power and includes afirst lens G1, a second lens G2, a third lens G3, and a fourth lens G4sequentially arranged from the magnified side to the minified side. Arefractive power of the first lens G1, a refractive power of the secondlens G2, a refractive power of the third lens G3, and a refractive powerof the fourth lens G4 are sequentially negative, negative, negative, andpositive. The second lens group 720 is disposed between the first lensgroup 710 and the minified side and has a positive refractive power.Besides, the second lens group 720 includes a fifth lens G5, a sixthlens G6, a seventh lens G7, an eighth lens G8, a ninth lens G9, and atenth lens G10 sequentially arranged from the magnified side to theminified side. A refractive power of the fifth lens G5, a refractivepower of the sixth lens G6, a refractive power of the seventh lens G7, arefractive power of the eighth lens G8, a refractive power of the ninthlens G9, and a refractive power of the tenth lens G10 are sequentiallypositive, positive, negative, positive, negative, and positive from themagnified side to the minified side.

In the embodiment, the position of the second lens group 720 in thefixed focal length lens 700 is fixed, and the first lens group 710 movesrelative to the second lens group 720 to focus. Namely, the first lensgroup 710 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 730 may be disposed on theminified side. The imaging process device 730 described in theembodiment is a light valve, and the light valve may be a DMD, an LCOSpanel, or a transmissive LCD, for instance. Besides, in the embodiment,the fixed focal length lens 700 is used to form an image provided by theimage processing device 730 at the magnified side.

In addition, as shown in FIG. 7, the fixed focal length lens 700described in the embodiment further includes an aperture stop ASdisposed between the eighth lens G8 and the ninth lens G9. A glass cover740 is further disposed between the image processing device 730 and thetenth lens G10 to protect the image processing device 730.

To ensure the optical imaging quality, the fixed focal length lens 700in the embodiment may satisfy 0.978<|f₁/f|<2.983 and 2.010<|f₂/f|<5.419.Here, f refers to an EFL of the fixed focal length lens 700, f₁ refersto an EFL of the first lens group 710, and f₂ refers to an EFL of thesecond lens group 720.

An embodiment of the fixed focal length lens 700 is given hereinafter.However, the invention is not limited to the data listed in Table 6.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 6 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 54.29 3.50 1.49 57.30 First lens S2 20.84 14.33 S342.49 2.00 1.80 55.00 Second lens S4 17.21 13.39 S5 −39.70 2.00 1.7837.60 Third lens S6 24.56 6.73 S7 −335.68 4.19 1.85 23.00 Fourth lens S8−47.96 Variable S9 33.76 8.37 1.62 43.40 Fifth lens S10 −61.44 13.63 S1122.26 4.71 1.51 54.20 Sixth lens S12 −20.24 3.30 1.83 37.20 Seventh lensS13 11.63 10.00 1.62 36.90 Eighth lens S14 −35.78 0.10 Aperture stop S1528.77 2.00 1.85 23.80 Ninth lens S16 14.18 7.06 1.49 79.70 Tenth lensS17 −20.16 21.50

In Table 6, the interval refers to a linear distance on the optical axisA between two adjacent surfaces. For instance, the interval of thesurface S1 refers to the linear distance on the optical axis A betweenthe surface S1 and the surface S2. The thickness, the refraction index,and the abbe number corresponding to each of the lenses listed in the“Notes” columns may be referred to as the corresponding values of theinterval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 720 in the fixed focal length lens 700 remains unchanged, and thefirst lens group 710 moves relative to the second lens group 720 tofocus. Therefore, the interval of the surface S8 is marked as“variable”, which indicates the linear distance on the optical axisbetween the surface S8 and the surface S9 is variable. According to anembodiment, when a projection distance is relatively short, the intervalof the surface S8 is 3.68 mm, for instance; according to anotherembodiment, when a projection distance is relatively long, the intervalof the surface S8 is 3.59 mm, for instance.

Moreover, in Table 6, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurfaces S9 and S10 are two surfaces of the fifth lens G5, the surfaceS11 is a surface of the sixth lens G6 facing the magnified side, thesurface S12 is a surface where the sixth lens G6 is connected to theseventh lens G7, the surface S13 is a surface where the seventh lens G7is connected to the eighth lens G8, and the surface S14 is a surface ofthe eight lens G8 facing the minified side. Here, the surface S14 isalso the place where the aperture stop AS is located. The surface S15 isa surface of the ninth lens G9 facing the magnified side, the surfaceS16 is a surface where the ninth lens G9 is connected to the tenth lensG10, and the surface S17 is surface of the tenth lens G10 facing theminified side. The numeral values of the parameters, such as thecurvature radius and the interval of each surface, are given in Table 6and thus will not be repeated hereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces andmay be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{1}} + {A_{2}y^{2}} + {A_{3}y^{3}} + {A_{4}y^{4}} + {A_{5}y^{5}} + {A_{6}y^{6}} + {A_{7}y^{7}} + {A_{8}y^{8}} + {A_{10}y^{10}} + {A_{11}y^{11}} + {A_{12}y^{12}} + {A_{13}y^{13}} + {A_{14}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S1 and S2 in Table 6) close to the optical axis A. K is a coniccoefficient, y is an aspheric height, and A₁ to A₁₄ are asphericcoefficients. The parameter values of the surfaces S1 and S2 are listedin Table 7.

TABLE 7 Aspheric Conic Coefficient Coefficient Coefficient CoefficientParameter Coefficient K A₁ A₂ A₃ A₄ S1  9.46E−01 −9.37E−03 3.30E−03−5.00E−04 2.49E−05 S2 −6.27E−01 −4.93E−03 4.61E−03 −3.96E−04 1.60E−05Aspheric Coefficient Coefficient Coefficient Coefficient ParameterCoefficient A₅ A₆ A₇ A₈ A₉ S1 3.14E−08 −2.58E−08 −3.97E−11  2.63E−11−1.17E−14 S2 2.39E−07 −1.53E−08  1.32E−10 −2.98E−11 −1.53E−13 AsphericCoefficient Coefficient Coefficient Coefficient Parameter CoefficientA₁₀ A₁₁ A₁₂ A₁₃ A₁₄ S1 −1.69E−14  1.44E−17 6.21E−18 2.90E−21 −1.11E−21S2 −5.64E−15 −1.34E−16 5.10E−17 7.36E−20 −2.69E−20

According to the present embodiment, it may be learned that the firstlens G1 is an aspheric lens and thus the first lens G1 may effectivelyresolve coma issues, astigmatism issues, or distortion issues of thefixed focal length lens 700. Besides, in the embodiment, the optimalrange of the EFL of the fixed focal length lens 700 is 7.84 mm to 8.02mm, which should however not be construed as a limitation to theinvention. Besides, the numerical aperture (F/#) ranges from 2.86 to2.88, and the viewing angle (2ω) is greater than 116.9°.

Moreover, the fixed focal length lens 700 described herein satisfiesF/H>0.52, where F is an EFL of the fixed focal length lens 700, and H isan image height. The definition of the image height H may be referred toas that depicted in FIG. 2 and thus will not be further describedhereinafter. If F/H>1, the viewing angle (2ω) of the fixed focal lengthlens 700 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 700 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

With reference to FIG. 7, in the first lens group 710 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, thethird lens G3 is a biconcave lens, and the fourth lens G4 is aconcave-convex lens with a convex surface facing the minified side. Eachof the second lens G2, the third lens G3, and the fourth lens G4 is aspherical lens, for instance. Due to the compensation resulting from theaspheric lens in the first lens group 710, at least the distortion issuemay be effectively resolved.

According to the embodiment, in the second lens group 720, each of thefifth lens G5, the sixth lens G6, the eighth lens G8, and the tenth lensG10 is a biconvex lens, the seventh lens G7 is a biconcave lens, and theninth lens G9 is a convex-concave lens with a convex surface facing themagnified side. In the second lens group 720, the sixth lens G6, theseventh lens G7, and the eighth lens G8 together form a triple cementedlens 722, and the ninth lens G9 and the tenth lens G10 together form adouble cemented lens 724. Thereby, the spherical aberration issue, thefield curvature issue, and the color aberration issue of the fixed focallength lens 700 may be effectively resolved. Moreover, the lenses in thesecond lens group 720 are all spherical lenses, for instance. Since thetenth lens G10 is the biconvex lens, the light at the minified side maybe effectively collected, and the collected light may pass through thelenses and be projected on the magnified side.

Fourth Embodiment

FIG. 8 is a schematic view illustrating a structure of a fixed focallength lens according to a fourth embodiment of the invention. Withreference to FIG. 8, the fixed focal length lens 800 is suitable forbeing disposed between a magnified side and a minified side, and thefixed focal length lens 800 has an optical axis A and includes a firstlens group 810 and a second lens group 820.

The first lens group 810 has a negative refractive power and includes afirst lens G1, a second lens G2, and a third lens G3 sequentiallyarranged from the magnified side to the minified side. A refractivepower of the first lens G1, a refractive power of the second lens G2,and a refractive power of the third lens G3 are sequentially negative,negative, and negative. The second lens group 820 is disposed betweenthe first lens group 810 and the minified side and has a positiverefractive power. Besides, the second lens group 820 includes a fourthlens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, an eighthlens G8, and a ninth lens G9 sequentially arranged from the magnifiedside to the minified side. A refractive power of the fourth lens G4, arefractive power of the fifth lens G5, a refractive power of the sixthlens G6, a refractive power of the seventh lens G7, a refractive powerof the eighth lens G8, and a refractive power of the ninth lens G9 aresequentially positive, positive, negative, positive, negative, andpositive from the magnified side to the minified side.

In the embodiment, the position of the second lens group 820 in thefixed focal length lens 800 is fixed, and the first lens group 810 movesrelative to the second lens group 820 to focus. Namely, the first lensgroup 810 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 830 may be disposed on theminified side. The imaging process device 830 described in the presentembodiment is a light valve, and the light valve may be a DMD, an LCOSpanel, or a transmissive LCD, for instance. Besides, in the presentembodiment, the fixed focal length lens 800 is used to form an imageprovided by the image processing device 830 at the magnified side.

In addition, as shown in FIG. 8, the fixed focal length lens 800described in the embodiment further includes an aperture stop ASdisposed between the seventh lens G7 and the eighth lens G8. A glasscover 840 is further disposed between the image processing device 830and the ninth lens G9 to protect the image processing device 830.

To ensure the optical imaging quality, the fixed focal length lens 800in the embodiment may satisfy 0.978<|f₁/f|<2.983 and 2.010<|f₂/f|<5.419.Here, f refers to an EFL of the fixed focal length lens 800, f₁ refersto an EFL of the first lens group 810, and f₂ refers to an EFL of thesecond lens group 820.

An embodiment of the fixed focal length lens 800 is given hereinafter.However, the invention is not limited to the data listed in Table 8.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 8 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 58.91 4.91 1.49 57.3 First lens S2 20.33 12.24 S354.53 2.21 1.70 48.9 Second lens S4 17.50 13.05 S5 −204.56 5.07 1.6456.2 Third lens S6 21.20 Variable S7 32.48 10.00 1.65 34.4 Fourth lensS8 −62.16 13.46 S9 18.65 4.52 1.50 61.8 Fifth lens S10 −21.96 6.32 1.7444.0 Sixth lens S11 9.36 8.32 1.59 62.1 Seventh lens S12 −39.24 3.57Aperture stop S13 35.13 2.77 1.76 27.6 Eighth lens S14 13.44 7.75 1.5163.1 Ninth lens S15 −20.54 17.66

In Table 8, the interval refers to a linear distance between twoadjacent surfaces on the optical axis A. For instance, the interval ofthe surface S1 refers to the linear distance on the optical axis Abetween the surface S1 and the surface S2. The thickness, the refractionindex, and the abbe number corresponding to each of the lenses listed inthe “Notes” columns may be referred to as the corresponding values ofthe interval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 820 in the fixed focal length lens 800 remains unchanged, and thefirst lens group 810 moves relative to the second lens group 820 tofocus. Therefore, the interval of the surface S6 is marked as“variable”, which indicates the linear distance on the optical axisbetween the surface S6 and the surface S7 is variable. According to anembodiment, when a projection distance is relatively short, the intervalof the surface S6 is 13.5 mm, for instance; according to anotherembodiment, when a projection distance is relatively long, the intervalof the surface S6 is 13.3 mm, for instance.

Moreover, in Table 8, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurface S9 is a surface of the fifth lens G5 facing the magnified side,the surface S10 is a surface where the fifth lens G5 is connected to thesixth lens G6, the surface S11 is a surface where the sixth lens G6 isconnected to the seventh lens G7, and the surface S12 is a surface ofthe seventh lens G7 facing the minified side. Here, the surface S12 isalso the place where the aperture stop AS is located. The surface S13 isa surface of the eighth lens G8 facing the magnified side, the surfaceS14 is a surface where the eighth lens G8 is connected to the ninth lensG9, and the surface S15 is surface of the ninth lens G9 facing theminified side. The curvature radius, the interval, and other parametersof each surface are shown in Table 8 and will not be further describedhereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces andmay be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{1}} + {A_{2}y^{2}} + {A_{3}y^{3}} + {A_{4}y^{4}} + {A_{5}y^{5}} + {A_{6}y^{6}} + {A_{7}y^{7}} + {A_{8}y^{8}} + {A_{10}y^{10}} + {A_{11}y^{11}} + {A_{12}y^{12}} + {A_{13}y^{13}} + {A_{14}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S1 and S2 in Table 8) close to the optical axis A. K is a coniccoefficient, y is an aspheric height, and A₁ to A₁₄ are asphericcoefficients. The parameter values of the surfaces S1 and S2 are listedin Table 9.

TABLE 9 Aspheric Conic Coefficient Coefficient Coefficient CoefficientParameter Coefficient K A₁ A₂ A₃ A₄ S1  0.946386 −9.37E−03 3.30E−03−5.00E−04 2.49E−05 S2 −0.62712 −4.93E−03 4.61E−03 −3.96E−04 1.60E−05Aspheric Coefficient Coefficient Coefficient Coefficient ParameterCoefficient A₅ A₆ A₇ A₈ A₉ S1 3.14E−08 −2.58E−08 −3.97E−11  2.63E−11−1.17E−14 S2 2.39E−07 −1.53E−08  1.32E−10 −2.98E−11 −1.53E−13 AsphericCoefficient Coefficient Coefficient Coefficient Parameter CoefficientA₁₀ A₁₁ A₁₂ A₁₃ A₁₄ S1 −1.69E−14  1.44E−17 6.21E−18 2.90E−21 −1.11E−21S2 −5.64E−15 −1.34E−16 5.10E−17 7.36E−20 −2.69E−20

According to the embodiment, it may be learned that the first lens G1 isan aspheric lens and thus the first lens G1 may effectively resolve comaissues, astigmatism issues, or distortion issues of the fixed focallength lens 800. Besides, in the embodiment, the optimal range of theEFL of the fixed focal length lens 800 is 7.72 mm to 7.8 mm, whichshould however not be construed as a limitation to the invention.Besides, the numerical aperture (F/#) ranges from 2.6 to 2.62, and theviewing angle (2ω) is greater than 116.7°.

Moreover, the fixed focal length lens 800 described herein satisfiesF/H>0.52, where F is an EFL of the fixed focal length lens 800, and H isan image height. The definition of the image height H may be referred toas that depicted in FIG. 2 and thus will not be further describedhereinafter. If F/H>1, the viewing angle (2ω) of the fixed focal lengthlens 800 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 800 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

With reference to FIG. 8, in the first lens group 810 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, andthe third lens G3 is a biconcave lens. Each of the second G2 and thethird lens G3 is a spherical lens, for instance. Due to the compensationresulting from the aspheric lens in the first lens group 810, at leastthe distortion issue may be effectively resolved.

According to the embodiment, in the second lens group 820, each of thefourth lens G4, the fifth lens G5, the seventh lens G7, and the ninthlens G9 is a biconvex lens, the sixth lens G6 is a biconcave lens, andthe eighth lens G8 is a convex-concave lens with a convex surface facingthe magnified side. In the second lens group 820, the fifth lens G5, thesixth lens G6, and the seventh lens G7 together form a triple cementedlens 822, and the eighth lens G8 and the ninth lens G9 together form adouble cemented lens 824. Thereby, the spherical aberration issue, thefield curvature issue, and the color aberration issue of the fixed focallength lens 800 may be effectively resolved. Moreover, the lenses in thesecond lens group 820 are all spherical lenses, for instance. Since theninth lens G9 is the biconvex lens, the light at the minified side maybe effectively collected, and the collected light may pass through thelenses and be projected on the magnified side.

Fifth Embodiment

FIG. 9 is a schematic view illustrating a structure of a fixed focallength lens according to a fifth embodiment of the invention. Withreference to FIG. 9, the fixed focal length lens 900 is suitable forbeing disposed between a magnified side and a minified side, and thefixed-focus lens 900 has an optical axis A and includes a first lensgroup 910 and a second lens group 920.

The first lens group 910 has a negative refractive power and includes afirst lens G1, a second lens G2, and a third lens G3 sequentiallyarranged from the magnified side to the minified side. A refractivepower of the first lens G1, a refractive power of the second lens G2,and a refractive power of the third lens G3 are sequentially negative,negative, and negative. The second lens group 920 is disposed betweenthe first lens group 910 and the minified side and has a positiverefractive power. Besides, the second lens group 920 includes a fourthlens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, an eighthlens G8, a ninth lens G9, and a tenth lens G10 sequentially arrangedfrom the magnified side to the minified side. A refractive power of thefourth lens G4, a refractive power of the fifth lens G5, a refractivepower of the sixth lens G6, a refractive power of the seventh lens G7, arefractive power of the eighth lens G8, a refractive power of the ninthlens G9, and a refractive power of the tenth lens G10 are sequentiallypositive, positive, positive, negative, positive, negative, and positivefrom the magnified side to the minified side.

In the embodiment, the position of the second lens group 920 in thefixed focal length lens 900 is fixed, and the first lens group 910 movesrelative to the second lens group 920 to focus. Namely, the first lensgroup 910 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 930 may be disposed on theminified side. The imaging process device 930 described in the presentembodiment is a light valve, and the light valve may be a DMD, an LCOSpanel, or a transmissive LCD, for instance. Besides, in the embodiment,the fixed focal length lens 900 is used to form an image provided by theimage processing device 930 at the magnified side.

In addition, as shown in FIG. 9, the fixed focal length lens 900described in the embodiment further includes an aperture stop ASdisposed between the eighth lens G8 and the ninth lens G9. A glass cover940 is further disposed between the image processing device 930 and thetenth lens G10 to protect the image processing device 930.

To ensure the optical imaging quality, the fixed focal length lens 900in the embodiment may satisfy 0.515<|f₁/f|<1.299 and 2.313<|f₂/f|<5.724.Here, f refers to an EFL of the fixed focal length lens 900, f₁ refersto an EFL of the first lens group 910, and f₂ refers to an EFL of thesecond lens group 920.

An embodiment of the fixed focal length lens 900 is given hereinafter.However, the invention is not limited to the data listed in Table 10.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 10 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 52.81 3.94 1.49 57.47 First lens S2 20.74 9.45 S351.76 3.00 1.49 57.40 Second lens S4 21.48 15.05 S5 −59.63 2.20 1.7538.95 Third lens S6 19.74 Variable S7 −76.49 7.89 1.76 27.58 Fourth lensS8 −39.36 7.72 S9 26.33 6.85 1.66 32.70 Fifth lens S10 −148.89 8.56 S1121.73 4.97 1.49 70.02 Sixth lens S12 −22.96 2.20 1.83 37.30 Seven lensS13 10.54 10.00 1.51 59.06 Eighth lens S14 −37.78 1.77 Aperture stop S1527.52 2.20 1.75 27.94 Ninth lens S16 14.65 4.14 1.50 69.47 Tenth lensS17 −20.01 21.42

In Table 10, the interval refers to a linear distance on the opticalaxis A between two adjacent surfaces. For instance, the interval of thesurface S1 refers to the linear distance on the optical axis A betweenthe surface S1 and the surface S2. The thickness, the refraction index,and the abbe number corresponding to each of the lenses listed in the“Notes” columns may be referred to as the corresponding values of theinterval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 920 in the fixed focal length lens 900 remains unchanged, and thefirst lens group 910 moves relative to the second lens group 920 tofocus. Therefore, the interval of the surface S6 is marked as“variable”, which indicates the linear distance on the optical axisbetween the surface S6 and the surface S7. According to an embodiment,when a projection distance is relatively short, the interval of thesurface S6 is 8.58 mm, for instance; according to another embodiment,when a projection distance is relatively long, the interval of thesurface S6 is 8.48 mm, for instance.

Moreover, in Table 10, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurfaces S9 and S10 are two surfaces of the fifth lens G5, the surfaceS11 is a surface of the sixth lens G6 facing the magnified side, thesurface S12 is a surface where the sixth lens G6 is connected to theseventh lens G7, the surface S13 is a surface where the seventh lens G7is connected to the eighth lens G8, and the surface S14 is a surface ofthe eight lens G8 facing the minified side. Here, the surface S14 isalso the place where the aperture stop AS is located. The surface S15 isa surface of the ninth lens G9 facing the magnified side, the surfaceS16 is a surface where the ninth lens G9 is connected to the tenth lensG10, and the surface S17 is surface of the tenth lens G10 facing theminified side. The curvature radius, the interval, and other parametersof each surface are shown in Table 10 and will not be further describedhereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces andmay be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{1}} + {A_{2}y^{2}} + {A_{3}y^{3}} + {A_{4}y^{4}} + {A_{5}y^{5}} + {A_{6}y^{6}} + {A_{7}y^{7}} + {A_{8}y^{8}} + {A_{10}y^{10}} + {A_{11}y^{11}} + {A_{12}y^{12}} + {A_{13}y^{13}} + {A_{14}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S1 and S2 in Table 10) close to the optical axis A. K is aconic coefficient, y is an aspheric height, and A₁ to A₁₄ are asphericcoefficients. The parameter values of the surfaces S1 and S2 are listedin Table 11.

TABLE 11 Aspheric Conic Coefficient Coefficient Coefficient CoefficientParameter Coefficient K A₁ A₂ A₃ A₄ S1  1.02E+00 −1.12E−03 1.92E−03−4.66E−04 2.47E−05 S2 −6.29E−01  4.60E−04 5.13E−03 −4.01E−04 1.62E−05Aspheric Coefficient Coefficient Coefficient Coefficient ParameterCoefficient A₅ A₆ A₇ A₈ A₉ S1 1.25E−08 −2.63E−08 −3.44E−11  2.67E−11−1.20E−14 S2 2.50E−07 −1.49E−08  1.40E−10 −2.96E−11 −1.52E−13 AsphericCoefficient Coefficient Coefficient Coefficient Parameter CoefficientA₁₀ A₁₁ A₁₂ A₁₃ A₁₄ S1 −1.70E−14  1.41E−17 6.17E−18 3.82E−21 −1.18E−21S2 −5.48E−15 −1.36E−16 5.08E−17 5.86E−20 −2.75E−20

According to the embodiment, it may be learned that the first lens G1 isan aspheric lens and thus the first lens G1 may effectively resolve comaissues, astigmatism issues, or distortion issues of the fixed focallength lens 900. Besides, in the embodiment, the optimal range of theEFL of the fixed focal length lens 900 is 7.93 mm to 7.96 mm, whichshould however not be construed as a limitation to the invention.Besides, the numerical aperture (F/#) is 2.79, and the viewing angle(2Ω) is greater than 116.6°.

The surfaces S3 and S4 of the second lens G2 are aspheric surfaces witheven power and may be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{4}} + {A_{2}y^{6}} + {A_{3}y^{8}} + {A_{4}y^{10}} + {A_{5}y^{12}} + {A_{6}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S3 and S4 in Table 11) close to the optical axis A. K is aconic coefficient, y is an aspheric height, and A₁ to A₆ are asphericcoefficients. The parameter values of the surfaces S3 and S4 are listedin Table 12.

TABLE 12 Conic Aspheric Coefficient Coefficient Coefficient CoefficientCoefficient Coefficient Coefficient Parameter K A₁ A₂ A₃ A₄ A₅ A₆ S3−3.49E+00 2.03E−05 −1.61E−08 −5.17E−12  1.84E−15 4.56E−18 4.58E−21 S4 1.27E−01 3.26E−05  2.14E−08  1.93E−10 −2.85E−13 1.39E−16 9.96E−18

Moreover, the fixed focal length lens 900 described herein satisfiesF/H>0.52, where F is an EFL of the fixed focal length lens 900, and H isan image height. The definition of the image height H may be referred toas that depicted in FIG. 2 and thus will not be further describedhereinafter. If F/H>1, the viewing angle (2ω) of the fixed focal lengthlens 900 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 900 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

With reference to FIG. 9, in the first lens group 910 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, andthe third lens G3 is a biconcave lens. Each of the first lens G1 and thesecond lens G2 is an aspheric lens, and the third lens G3 is a sphericallens, for instance. Due to the compensation resulting from the asphericlens in the first lens group 910, at least the distortion issue may beeffectively resolved.

According to the embodiment, in the second lens group 920, the fourthlens G4 is a concave-convex lens with a convex surface facing theminified side, each of the fifth lens G5, the sixth lens G6, the eighthlens G8, and the tenth lens G10 is a biconvex lens, the seventh lens G7is a biconcave lens, and the ninth lens G9 is a convex-concave lens witha convex surface facing the magnified side. In the second lens group920, the sixth lens G6, the seventh lens G7, and the eighth lens G8together form a triple cemented lens 922, and the ninth lens G9 and thetenth lens G10 together form a double cemented lens 924. Thereby, thespherical aberration issue, the field curvature issue, and the coloraberration issue of the fixed focal length lens 900 may be effectivelyresolved. Moreover, the lenses in the second lens group 920 are allspherical lenses, for instance. Since the tenth lens G10 is the biconvexlens, the light at the minified side may be effectively collected, andthe collected light may pass through the lens and be projected on themagnified side.

The Sixth Embodiment

FIG. 10 is a schematic view illustrating a structure of a fixed focallength lens according to a sixth embodiment of the invention. Withreference to FIG. 10, the fixed focal length lens 500 is suitable forbeing disposed between a magnified side and a minified side, and thefixed focal length lens 500 has an optical axis A and includes a firstlens group 510 and a second lens group 520.

The first lens group 510 has a negative refractive power and includes afirst lens G1, a second lens G2, and a third lens G3 sequentiallyarranged from the magnified side to the minified side. A refractivepower of the first lens G1, a refractive power of the second lens G2,and a refractive power of the third lens G3 are sequentially negative,negative, and negative. The second lens group 520 is disposed betweenthe first lens group 510 and the minified side and has a positiverefractive power. Besides, the second lens group 520 includes a fourthlens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, an eighthlens G8, a ninth lens G9, a tenth lens G10, an eleventh lens G11, and atwelfth lens G12 sequentially arranged from the magnified side to theminified side. A refractive power of the fourth lens G4, a refractivepower of the fifth lens G5, a refractive power of the sixth lens G6, arefractive power of the seventh lens G7, a refractive power of theeighth lens G8, a refractive power of the ninth lens G9, a refractivepower of the tenth lens G10, a refractive power of the eleventh lensG11, and a refractive power of the twelfth lens G12 are sequentiallypositive, positive, negative, positive, positive, negative, positive,negative, and positive from the magnified side to the minified side.

In the embodiment, the position of the second lens group 520 in thefixed focal length lens 500 is fixed, and the first lens group 510 movesrelative to the second lens group 520 to focus. Namely, the first lensgroup 510 is a focusing lens group suitable for conducting afocus-adjusting compensation at different projection distances.

Generally, an image processing device 530 may be disposed on theminified side. The imaging process device 530 described in theembodiment is a light valve, and the light valve may be a DMD, an LCOSpanel, or a transmissive LCD, for instance. Besides, in the embodiment,the fixed focal length lens 500 is used to form an image provided by theimage processing device 530 at the magnified side.

In addition, as shown in FIG. 10, the fixed focal length lens 500described in the embodiment further includes an aperture stop ASdisposed between the tenth lens G10 and the eleventh lens G11. A glasscover 540 is further disposed between the image processing device 530and the twelfth lens G12 to protect the image processing device 530.

To ensure the optical imaging quality, the fixed focal length lens 500in the embodiment may satisfy 0.515<|f₁/f|<1.299 and 2.313<|f₂/f|<5.724.Here, f refers to an EFL of the fixed focal length lens 500, f₁ refersto an EFL of the first lens group 510, and f₂ refers to an EFL of thesecond lens group 520.

An embodiment of the fixed focal length lens 500 is given hereinafter.However, the invention is not limited to the data listed in Table 13.People having ordinary skill in the art may be able to properly modifythe parameters or the configuration of the invention in view of theinvention without departing from the scope or spirit of the invention.

TABLE 13 Curvature Interval Refraction Abbe Surface Radius (mm) (mm)Index Number Notes S1 104.70 4.00 1.49 57.47 First lens S2 19.76 15.45S3 43.00 2.20 1.74 44.78 Second lens S4 19.46 15.00 S5 −66.87 1.70 1.7444.78 Third lens S6 24.97 Variable S7 93.35 8.00 1.62 35.70 Fourth lensS8 −49.22 3.20 S9 25.97 7.20 1.54 45.78 Fifth lens S10 −6456.45 8.15 S1142.45 1.60 1.74 44.78 Sixth lens S12 11.28 1.10 S13 14.95 3.20 1.5840.74 Seventh lens S14 35.32 0.12 S15 18.81 4.75 1.54 45.78 Eighth lensS16 −12.86 6.20 1.83 37.29 Ninth lens S17 27.44 2.75 1.51 64.16 Tenthlens S18 −18.88 1.85 Aperture stop S19 47.38 0.80 1.85 32.17 Eleventhlens S20 13.91 3.70 1.49 81.61 Twelfth lens S21 −15.31 21.50

In Table 13, the interval refers to a linear distance on the opticalaxis A between two adjacent surfaces. For instance, the interval of thesurface S1 refers to the linear distance on the optical axis A betweenthe surface S1 and the surface S2. The thickness, the refraction index,and the abbe number corresponding to each of the lenses listed in the“Notes” columns may be referred to as the corresponding values of theinterval, the refraction index, and the abbe number listed in thecorresponding rows. In the embodiment, the position of the second lensgroup 520 in the fixed focal length lens 500 remains unchanged, and thefirst lens group 510 moves relative to the second lens group 520 tofocus. Therefore, the interval of the surface S6 is marked as“variable”, which indicated the linear distance on the optical axisbetween the surface S6 and the surface S7 is variable. According to anembodiment, when a projection distance is relatively short, the intervalof the surface S6 is 17.48 mm, for instance; according to anotherembodiment, when a projection distance is relatively long, the intervalof the surface S6 is 17.41 mm, for instance.

Moreover, in Table 13, the surfaces S1 and S2 are two surfaces of thefirst lens G1, the surfaces S3 and S4 are two surfaces of the secondlens G2, the surfaces S5 and S6 are two surfaces of the third lens G3,the surfaces S7 and S8 are two surfaces of the fourth lens G4, thesurfaces S9 and S10 are two surfaces of the fifth lens G5, the surfacesS11 and S12 are two surfaces of the sixth lens G6, the surfaces S13 andS14 are two surfaces of the seventh lens G7, the surface S15 is asurface of the eighth lens G8 facing the magnified side, the surface S16is a surface where the eighth lens G8 is connected to the ninth lens G9,the surface S17 is a surface where the ninth lens G9 is connected to thetenth lens G10, and the surface S18 is a surface of the tenth lens G10facing the minified side. Here, the surface S18 is also the place wherethe aperture stop AS is located. The surface S19 is a surface of theeleventh lens G11 facing the magnified side, the surface S20 is asurface where the eleventh lens G11 is connected to the twelfth lensG12, and the surface S21 is surface of the twelfth lens G12 facing theminified side. The numeral values of the parameters, such as thecurvature radius and the interval of each surface, are given in Table 13and thus will not be repeated hereinafter.

The surfaces S1 and S2 of the first lens G1 are aspheric surfaces witheven power and may be represented by the following formula:

$Z = {\frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}y^{2}}}} + {A_{1}y^{4}} + {A_{2}y^{6}} + {A_{3}y^{8}} + {A_{4}y^{10}} + {A_{5}y^{12}} + {A_{6}y^{14}}}$

Similarly, in the formula, Z is a sag in the direction of the opticalaxis A, and c is the inverse of the radius of an osculating sphere, i.e.the inverse of the curvature radii (e.g., the curvature radii of thesurfaces S1 and S2 in Table 13) close to the optical axis A. K is aconic coefficient, y is an aspheric height, and A₁ to A₆ are asphericcoefficients. The parameter values of the surfaces S1 and S2 are listedin Table 14.

TABLE 14 Conic Aspheric Coefficient Coefficient Coefficient CoefficientCoefficient Coefficient Coefficient Parameter K A₁ A₂ A₃ A₄ A₅ A₆ S1 4.53E+00 1.37E−05 −2.40E−08  2.59E−11 −1.60E−14 5.55E−18 −7.90E−22 S2−5.85E−01 1.57E−05 −6.30E−09 −4.00E−11  1.26E−14 2.61E−17 −3.00E−20

According to the embodiment, it may be learned that the first lens G1 isan aspheric lens and thus the first lens G1 may effectively resolve comaissues, astigmatism issues, or distortion issues of the fixed focallength lens 500. Besides, in the embodiment, the optimal range of theEFL of the fixed focal length lens 500 is 6.41 mm to 6.47 mm, whichshould however not be construed as a limitation to the invention.Besides, the numerical aperture (F/#) ranges from 2.79 to 2.91, and theviewing angle (2ω) is greater than 125.5°.

Moreover, the fixed focal length lens 500 described herein satisfiesF/H>0.52, where F is an EFL of the fixed focal length lens 500, and H isan image height. The definition of the image height H may be referred toas that depicted in FIG. 2 and thus will not be further describedhereinafter. If F/H>1, the viewing angle (2Ω) of the fixed focal lengthlens 500 is less than 90°. At this time, the projection angle is notconsidered as a wide angle, and thus the imaging quality is notnegatively affected even though the first lens G1 described herein isnot an aspheric lens. However, if F/H<0.52, the viewing angle (2ω) ofthe fixed focal length lens 500 is greater than 140°; therefore, moreaspheric lenses and other lenses are required to compensate theaberration.

With reference to FIG. 10, in the first lens group 510 described in theembodiment, each of the first lens G1 and the second lens G2 is aconvex-concave lens with a convex surface facing the magnified side, andthe third lens G3 is a biconcave lens. Each of the second G2 and thethird lens G3 is a spherical lens, for instance. Due to the compensationresulting from the aspheric lens in the first lens group 510, at leastthe distortion issue may be effectively resolved.

According to the embodiment, in the second lens group 520, each of thefourth lens G4, the fifth lens G5, the eighth lens G8, the tenth lensG10, and the twelfth lens G12 is a biconvex lens, each of the sixth lensG6 and the eleventh lens G11 is a convex-concave lens with a convexsurface facing the magnified side, the seventh lens G7 is aconcave-convex lens with a convex surface facing the magnified side, andthe ninth lens G9 is a biconcave lens. In the second lens group 520, theeighth lens G8, the ninth lens G9, and the tenth lens G10 together forma triple cemented lens 522, and the eleventh lens G11 and the twelfthlens G12 together form a double cemented lens 524. Thereby, thespherical aberration issue, the field curvature issue, and the coloraberration issue of the fixed focal length lens 500 may be effectivelyresolved. Moreover, the lenses in the second lens group 520 are allspherical lenses, for instance. Since the twelfth lens G12 is thebiconvex lens, the light at the minified side may be effectivelycollected, and the collected light may pass through the lens and beprojected on the magnified side.

To sum up, at least one of the following advantages or effects may beachieved according to the embodiments of the invention. As describedabove, the lens groups of the optical lens at most include twelve lensesand at least include nine lenses. Accordingly, compared to theconventional lens, the optical lens provided herein has the reducednumber of lenses and thus has the simplified design. Moreover, the firstlens described in the embodiments of the invention is the aspheric lens,which may effectively resolve the distortion issues of the fixed focallength lens. By contrast, all the lenses other than the first lens maybe spherical lenses, and thereby the manufacturing costs may beeffectively lowered down.

The foregoing description of the embodiments of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formor to exemplary embodiments disclosed. Accordingly, the foregoingdescription should be regarded as illustrative rather than restrictive.Obviously, many modifications and variations will be apparent topractitioners skilled in this art. The embodiments are chosen anddescribed in order to best explain the principles of the invention andits best mode practical application, thereby to enable persons skilledin the art to understand the invention for various embodiments and withvarious modifications as are suited to the particular use orimplementation contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto and their equivalentsin which all terms are meant in their broadest reasonable sense unlessotherwise indicated. Therefore, the term “the invention”, “theinvention” or the like does not necessarily limit the claim scope to aspecific embodiment, and the reference to particular exemplaryembodiments of the invention does not imply a limitation on theinvention, and no such limitation is to be inferred. The invention islimited only by the spirit and scope of the appended claims. Theabstract of the disclosure is provided to comply with the rulesrequiring an abstract, which will allow a searcher to quickly ascertainthe subject matter of the technical disclosure of any patent issued fromthis disclosure. It is submitted with the understanding that it will notbe used to interpret or limit the scope or meaning of the claims. Anyadvantages and benefits described may not apply to all embodiments ofthe invention. It should be appreciated that variations may be made inthe embodiments described by persons skilled in the art withoutdeparting from the scope of the invention as defined by the followingclaims. Moreover, no element and component in the present disclosure isintended to be dedicated to the public regardless of whether the elementor component is explicitly recited in the following claims.

What is claimed is:
 1. An optical lens comprising: a first lens groupdisposed between a magnified side and a minified side, the first lensgroup having a negative refractive power; and a second lens groupdisposed between the first lens group and the minified side, the secondlens group having a positive refractive power, wherein the optical lensis capable of forming an image at the magnified side, wherein F/H>0.52,F is an effective focal length, and H is an image height, wherein aviewing angle is greater than 116.7 degrees.
 2. The optical lens asrecited in claim 1, wherein the first lens group comprises a first lens,a second lens, and a third lens sequentially arranged from the magnifiedside to the minified side, a refractive power of the first lens, arefractive power of the second lens, and a refractive power of the thirdlens are sequentially negative, negative, and negative from themagnified side to the minified side, the first lens is an aspheric lens,the second lens group comprises a fourth lens, a fifth lens, a sixthlens, a seventh lens, an eighth lens, a ninth lens, and a tenth lenssequentially arranged from the magnified side to the minified side, arefractive power of the fourth lens, a refractive power of the fifthlens, a refractive power of the sixth lens, a refractive power of theseventh lens, a refractive power of the eighth lens, a refractive powerof the ninth lens, and a refractive power of the tenth lens aresequentially positive, positive, positive, negative, positive, negative,and positive from the magnified side to the minified side.
 3. Theoptical lens as recited in claim 2, wherein each of the first lens, thesecond lens, and the ninth lens is a convex-concave lens with a convexsurface facing the magnified side, each of the third lens and theseventh lens is a biconcave lens, the fourth lens is a concave-convexlens with a convex surface facing the minified side, and each of thefifth lens, the sixth lens, the eighth lens, and the tenth lens is abiconvex lens.
 4. The optical lens as recited in claim 2, wherein thesecond lens is an aspheric lens.
 5. The optical lens as recited in claim2, wherein each of the first lens, the second lens, and the ninth lensis a convex-concave lens with a convex surface facing the magnifiedside, each of the third lens and the seventh lens is a biconcave lens,each of the fourth lens, the fifth lens, the sixth lens, and the tenthlens is a biconvex lens, and the eighth lens is a concave-convex lenswith a convex surface facing the magnified side.
 6. The optical lens asrecited in claim 2, wherein the tenth lens is an aspheric lens.
 7. Theoptical lens as recited in claim 2, wherein the sixth lens, the seventhlens, and the eighth lens together form a triple cemented lens, and theninth lens and the tenth lens together form a double cemented lens. 8.The optical lens as recited in claim 1, wherein the first lens groupcomprises a first lens, a second lens, and a third lens sequentiallyarranged from the magnified side to the minified side, a refractivepower of the first lens, a refractive power of the second lens, and arefractive power of the third lens are sequentially negative, negative,and negative from the magnified side to the minified side, the firstlens is an aspheric lens, the second lens group comprises a fourth lens,a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninthlens, a tenth lens, an eleventh lens, and a twelfth lens sequentiallyarranged from the magnified side to the minified side, a refractivepower of the fourth lens, a refractive power of the fifth lens, arefractive power of the sixth lens, a refractive power of the seventhlens, a refractive power of the eighth lens, a refractive power of theninth lens, a refractive power of the tenth lens, a refractive power ofthe eleventh lens, and a refractive power of the twelfth lens aresequentially positive, positive, negative, positive, positive, negative,positive, negative, and positive from the magnified side to the minifiedside.
 9. The optical lens as recited in claim 8, wherein each of thefirst lens, the second lens, the sixth lens, and the eleventh lens is aconvex-concave lens with a convex surface facing the magnified side,each of the third lens and the ninth lens is a biconcave lens, each ofthe fourth lens, the fifth lens, the eighth lens, the tenth lens, andthe twelfth lens is a biconvex lens, and the seventh lens is aconcave-convex lens with a convex surface facing the magnified side. 10.The optical lens as recited in claim 8, wherein the eighth lens, theninth lens, and the tenth lens together form a triple cemented lens, andthe eleventh lens and the twelfth lens together form a double cementedlens.
 11. The optical lens as recited in claim 1, wherein an effectivefocal length of the optical lens is f, an effective focal length of thefirst lens group is f₁, an effective focal length of the second lensgroup is f₂, and the optical lens satisfies 0.515<|f₁/f|<1.299 and2.313<|f₂/f|<5.724.
 12. The optical lens as recited in claim 1, whereinthe first lens group comprises a first lens, a second lens, a thirdlens, and a fourth lens sequentially arranged from the magnified side tothe minified side, a refractive power of the first lens, a refractivepower of the second lens, a refractive power of the third lens, and arefractive power of the fourth lens are sequentially negative, negative,negative, and positive from the magnified side to the minified side, thefirst lens is an aspheric lens, the second lens group comprises a fifthlens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and atenth lens sequentially arranged from the magnified side to the minifiedside, a refractive power of the fifth lens, a refractive power of thesixth lens, a refractive power of the seventh lens, a refractive powerof the eighth lens, a refractive power of the ninth lens, and arefractive power of the tenth lens are sequentially positive, positive,negative, positive, negative, and positive from the magnified side tothe minified side.
 13. The optical lens as recited in claim 12, whereineach of the first lens, the second lens, and the ninth lens is aconvex-concave lens with a convex surface facing the magnified side,each of the third lens and the seventh lens is a biconcave lens, thefourth lens is a concave-convex lens with a convex surface facing theminified side, and each of the fifth lens, the sixth lens, the eighthlens, and the tenth lens is a biconvex lens.
 14. The optical lens asrecited in claim 12, wherein the sixth lens, the seventh lens, and theeighth lens together form a triple cemented lens, and the ninth lens andthe tenth lens together form a double cemented lens.
 15. The opticallens as recited in claim 1, wherein the first lens group comprises afirst lens, a second lens, and a third lens sequentially arranged fromthe magnified side to the minified side, a refractive power of the firstlens, a refractive power of the second lens, and a refractive power ofthe third lens are sequentially negative, negative, and negative fromthe magnified side to the minified side, the first lens is an asphericlens, the second lens group comprises a fourth lens, a fifth lens, asixth lens, a seventh lens, an eighth lens, and a ninth lenssequentially arranged from the magnified side to the minified side, arefractive power of the fourth lens, a refractive power of the fifthlens, a refractive power of the sixth lens, a refractive power of theseventh lens, a refractive power of the eighth lens, and a refractivepower of the ninth lens are sequentially positive, positive, negative,positive, negative, and positive from the magnified side to the minifiedside.
 16. The optical lens as recited in claim 15, wherein each of thefirst lens, the second lens, and the eighth lens is a convex-concavelens with a convex surface facing the magnified side, each of the thirdlens and the sixth lens is a biconcave lens, and each of the fourthlens, the fifth lens, the seventh lens, and the ninth lens is a biconvexlens.
 17. The optical lens as recited in claim 15, wherein the fifthlens, the sixth lens, and the seventh lens together form a triplecemented lens, and the eighth lens and the ninth lens together form adouble cemented lens.
 18. The optical lens as recited in claim 1,wherein an effective focal length of the optical lens is f, an effectivefocal length of the first lens group is f₁, an effective focal length ofthe second lens group is f₂, and the optical lens satisfies0.978<|f₁/f|<2.983 and 2.010<|f₂/f|<5.419.
 19. The optical lens asrecited in claim 1, wherein the second lens group further comprises anaperture stop.
 20. An optical lens comprising: a first lens groupdisposed between a magnified side and a minified side, the first lensgroup having a negative refractive power; and a second lens groupdisposed between the first lens group and the minified side, the secondlens group having a positive refractive power, wherein the optical lensis capable of forming an image at the magnified side, wherein0.627>F/H>0.52, F is an effective focal length, and H is an imageheight.